When two dams containing the waste water from an iron ore mine in Brazil recently burst and spewed its contents into the local river, it created what some are calling Brazil’s worst ever environmental disaster. At least 11 people were killed, and the environment has been seriously polluted. Two weeks later, the toxic sludge containing mercury, arsenic, chromium and manganese has traveled 500 kilometers (310 miles) downstream, reaching the Atlantic Ocean.

It was on November 5 that two dams holding an estimated 60 million cubic meters (2.1 billion cubic feet) of waste water, or tailings, from an iron ore mine operated by the company Samarco failed, devastating the two local communities. While the details of what caused the fail are currently unclear, 11 deaths are so far confirmed, and 15 people are still missing. Over 600 others had their homes washed away, as the wall of water and mud ripped through their villages. But apart from the terrible humanitarian disaster, it has also created a massive environmental one too, as the toxic sludge made its way into the Rio Doce estuary.

So far, the drinking water for an estimated 250,000 people has been contaminated, while those living directly on the river have been advised not to wash themselves or their clothes in the now muddy orange water. Samarco, owned by the mining giants Vale and BHP Billiton, has deployed 9,000 meters (30,000 feet) of floating barriers along both banks of the river to try and protect the wildlife that call the region home. They’ve also been dredging the estuary of the river in the hope that they can increase the rate of flow so that the toxic water will be washed out and diluted at sea.

This, however, does nothing for the plants and animals already living in the river, of which there are probably very few left. Teams of biologists have already attempted to try and save some of this wildlife, by removing as many fish as possible and housing them in 1,000-liter (1,760-pint) tanks before transporting them to safer lakes. But it seems it is too late for some, as Aloysio da Silva Ferrão Filho, a researcher from the Oswaldo Cruz Foundation told the magazine Chemistry World: “The biodiversity of the river is completely lost. Several species, including endemic ones must be extinct.”

The next worry, though, is the impact that the sludge will have on the wildlife in the Atlantic. Environmentalists are worried that if the winds and tides take the toxic mud north, then the Abrolhos Marine National Park could be at risk. The park contains an archipelago of islands and reefs that are a hotspot for marine life, including turtles, dolphins and whales. As the disaster hit after turtles nested near the mouth of the river, their eggs have already been removed and buried on higher ground.

So far, while maintaining that the sludge is harmless, Samarco has agreed to pay $250 million (£165 million) in fines to the Brazilian government. But as the chemicals contained in the mud cause it to harden, some warn that the catastrophe could alter the entire course of the river, while the contaminants could impact the environment for generations to come.